Cell signalling by ion channels Flashcards
what is another name for ligand-gated ion channels?
ionotropic receptors
what is a ligand-gated ion channel?
A multi-subunit protein that crosses through the plasma membrane
- the channel may be closed or open
how do molecules move through ligand-gated ion channels?
when open ions move into, or out of, the cell depending on their electrochemical gradient
what determines the ion that can move through a ligand-gated ion channel?
the type of ion(s) moving through the channel is determined by the channel’s structure
what are some stimuli that can open ligand-gated ion channels?
- changes in voltage across the membrane
- deformation of the membrane
- ligands at the cell surface
-some channels are always open
- a further class of ion channel are opened in response to internal signals
what are GIRK’s and what is their function?
G-protein gated inwardly-rectifying potassium channels
- they allow K+ to move out of a cell
what signals do ligand-gated ion channels provide?
rapid and normally short lasting signals to cells
particularly well suited to signalling in the nervous system
what is the structure of ligand-gated ion channels?
-channels are composed of multiple subunits
- 4 to 5, the number depending on the channel type
- each protein subunit makes 4 passes across the membrane
what is the most important ligand-gated receptor?
receptor at the neuromuscular junction
what is the receptor at the neuromuscular junction?
nicotinic acetylcholine receptor
what is the structure of the nicotinic acetylcholine receptor?
made up of 5 subunits
found in different regions and these have different subunit structures
what is the function of the nicotinic acetylcholine receptor?
influx of Na+ causes the muscle to depolarize
where are nicotinic acetylcholine receptors found?
present in the brain and elsewhere
how does the acetylcholine receptor function?
as part of a complex with other proteins
what is rapsyn?
anchors the nicotinic acetylcholine receptor to the membrane
what is the function of rapsyn?
concentrates the nAChR at the correct location opposite the synapse
how does being in a complex help the nicotinic acetylcholine receptor?
complex involved in correctly maintaining the positioning of the receptor for most effective functioning
what does loss of dystrophin result in?
Duchenne Muscular Dystrophy, an X-linked muscle wasting disorder
what are the two types of glutamate receptors present at some synapses?
AMPA receptors
NMDA receptors
what is an AMPA receptor?
ion channels that allow Na+ into the post-synaptic target cell
what is an NMDA receptor?
ion channels that allow Ca2+ into the post-synaptic target cell
what happens when Ca2+ enters the post-synaptic target cell?
an increase in Ca2+ can stimulate multiple cellular events including protein kinases
what happens when kinases are activated in the post-synaptic target cell?
activation of kinases (including CaMKII) can mediate many intracellular actions
what is the function of the protein kinase CaMKII?
CaMKII plays an important role in long term potentiation (a mechanism involved in memory formation)
